Refining of mineral oils



Oct. 26, 1943. 'w l-L RUPP 2,332,814

REFINING OF MINERAL OILS F'iiled July 2, 1941 Co MDE vs A 'rE Patented Oct. 26, `1943 Walter H. Rupp, Mountainside, N'. J.,assignor to- Standard Oil Development Gomp'anyf,i a. corpo` ration of Delaware Application-2mg 2; 1941, smarNmenonzr 5 Claims.

The: present invention is concerned withi the refining of? mineral oils. Therinvention4 i'simore particularly concerned with. the recovery of hydrocarbon gases which are evolved during the processing and storage of petroleum oils boiling in the Vmotor fuelc boiling range" The invention is especiallyconcernedwith a method of recoveriing these valiiablrhydrocarbon constituents'in a manner.' thatlthe-liaz/ard ot? ani explosion iseli'm'sinated.

Inathef refining of mineral oils, particularly in the: productioni and? marketing of petroleum oils boiling inthe-motor filelfboilingrange, it is necessaryto store these oils'in relatively large storage tanks i'ntowlicli: a considerable quantity of' air isV drawn andi from whichV an appreciable: quantity of` gas is expelled; The gases expelledl in the breathing"oill theztankccmprise: amelativeiyhigh concentration of, valuable `hydrocarbon constituents; Forexample; the'gase's'expelled ironia-tankinW-hich-amotor fuel having a vapor pressurein the rangeifrorn4 about 450 to 600 mm. ot mercury at 100 F., and in;whi1:;hfr the oil temperature is \1'00?F., comprise approximately 55% to '70% of hydrocarbon constituents; Since the' atmospheric' "temperature passes through a' cycle cha-ngelr every day; the loss in' oil due to'- tank breathing" over* arelativeiy short' time is` appreciable.Furthermore sinc'e the `re1` ativel'y lowerboilin-g-"nrore valuable'hydrocarbon constituentsare initially' lost, the vquality ofthe remaining oilis also impaired.

In order t'o overcome these' disa'dvantag'esi.it`

has been proposed that the. gases which., are; ex"` hald be` compressed and? retnrnedltoA tefstorage, vessell. However, a4 process. ofthis. character not.. satisfactory orf, the reason that; althoughA the. gases removed` from, thestorage vessel' may be.

Weill outside the, explosive. liirit): the explosion.

hazard is-materially increasedby compressingthe, gases inV orderl to condense the` same.- I have,T

however, now. discovered aprocesswhichl may be,` readily adapted toA the. recoveryy t oi gases:evolved` from storage yvesselsinfthe, abovendescribed man.-`

ner, which entirely eliminates.the;explosionihaz,1`

ardinovvE encountered. 4ln accordance vvitht my process; the vapors: which. are removed from the storage vessel andl which. contain af. relatively` high concentrationfonain arefcompressed to conf dense-andirecoven theoilfconstituents. However' ini order tm eliminate; theexplosiomhaZa-rd Izsegf regate a portion;ottherlowenboilingghydrocarbon; constituentslfrom .the ,compressoncondensateranrl pass the; segregatedstreaxm into` the: exliaieezl;viewd porousstreampassing. from the storage" vessel toitlie compressi'orrzonea- 'Illie processL of:` my-y inventiorr may` bel readilst4 understood'rbyf reference toitlie drawingf'llxsh trating-`r ani ernbodirnent2 ofr thief same. For' trie pur-poset ori' description; it is=` assumed* thatitheir petroleum oil stored islaipetroleumf oilZ boilingini` thel motorV 'uelf boiling" ranger, is also assumedl tha-tfy the; vessell c'omprises a conventional storage*A tanlrv andi that*- the*z vessell iis approximately' half' fiill of the: petroleum oil As the atlnospllerio= temperatuoedropssasiisnormally il'iejcasediringl of-"tien storage vessol Ii are 'cooled andi contract;V

I. resultingsin freshai'n'beingi iniiaiedintoitli'e t'ank by meanssof valves or.' li'n 2i Erthermmeg. the? temperature oiithe oil; vpantioulamly the s temper atureicff the` upper" oillayen iin contact vs'fithntree vapors, is"` Iorverecl;A resulting' in: at lower vapor' pressure and a further inhaling: off' fresh ain' Thus,",the. extent to,whichtlievaporsinitlieupper partt off the? st'orage'-` vessel;Y which; comprise maf--4 drooarbon oonstituents;A contract is: also a2- directifnctionzof the vapori-pressure ofi tlieoila. During# the ri's'e'V in atmosphenim. temperamreg. the: vapor" pressure off' the oillincreases,y remlting.' in adde tional`l oil being vaporizedi- The?. vaponsini then.

upper pantofi4 the' `storage tank:v also exlpandt anni;

boiling hydrocarbon constituents. and. to. removal' by,` means of4 line l2 the. relatively higher; boiling` constituents fwhichareireturned tostoragezonef If., I

AIn accordance:withimwprooesslthe lower boil-- ing-hydrocarbom constituents removed n loroV meansY o;f` line: l 3- are: introducedA into xthe=stream passing: from the storageizoneto the compressiomzone.`

Under certain conditions, depending upon@ the;- compositioniofrthe'vaporss passing fromitheiston' age; zone: tof theg'compression: zone/itt` mightrbef desirable. to.-utilize onlvf.'v at portion; o fs the: vapors. removed overheadifroxnxzoxfie l0.. 'Ithisfconrlition may exist when the temperature cycle is relatively high, resulting in the expelling of a relatively large quantity of hydrocarbon vapors. If this operation be desirable, the remaining portion of the vapors removed overhead from zone l are removed by means of line ll and handled or disposed of in any manner desirable. Under certain conditions as, for example, when a relatively small am'oun't'oi hydrocarbon vapors f are evolved from the storage zone, it may be de sirable to add a quantity of relatively low boiling hydrocarbon constituents secured from an external sourcev which are introduced into the systemA by means of line I5. The process of the present invention maybe widely varied. The invention-essentially comprises segregating relatively low boiling hydro- Operation 1 (Recycle of segregated constituents' carbon constituents from the condenser conden.V

sate and introducing these segregated hydrocarbon constituents into the stream flowing fromv 100 pounds to 500 pounds per square inch gauge,4

and generally operated at a pressure in the range from ab0ut250 to 400 pounds per square inch gauge. Thetemperature maintained in the separation zone may vary considerably but will generally be in the range lfrom about40 F. to 120ic F. FOreXampIe, Vwhen the V'storage oil comprises a petro-leumoil boiling in the motor fuel boiling range, the 4 temperature maintained in the compression zone is generally in the range froml about 60 F. to about 80 F. A

`The amountof relatively low boiling hydrocarbon constituents circulated to the ycompression zone along with the feed gases to the compression zonewillvary considerably depending upon the characterrof the vaporsv evolved.` In general, the amountcirculated is to increase the hydrocarbonconstituent concentration so that it will be well above the explosive limits. I Ihave* pression zone is inthe range from about 5% to 50% Vby volume, preferably between 15% to 30% by volume, based upon the total tank vapors.,

In order to illustrate my invention further, the following example is givenvwhich should not be construed as limiting the same in anymanner whatsoever.

Example The vapors evolved from a storage tankV in which motor gasoline is stored at 100 F., which gasoline has a vapor pressure of 540 mm. of mercury, comprise about 35% air by volume. The remainder comprises hydrocarbon fractions which are recoverable.

The lower explosive llimit forthe hydrocarbons contained in the vapors in equilibrium with the gasoline is about 1.5 mol percent, vwhile the upper limit is about 8.0 mol percent. Thus, it is desirable to maintain the concentration of hydrocarbons without the range of 1.5 to 8.0 mol percent. f Y l Y In recovering vas liquid the valuable vaporous hydrocarbon fractions by compression and subsequent cooling,` the vresidue gas stream will ordinarily increase-in aircontent and enter the ex- .75

plosive limit range. However, I have discovered that this may readily be avoided without decreasing gasoline recovery providing the liquid condensate be segregated and a portion of the same recycled as described. This is readily apparent by the following data in which in one cp- 'eration recycle of segregated condensate constituents was not employed, while ina second operation recycle of these constituents was employed.

not employed) I Residue gas Recovered Tarik vapors after comgasoline after pression compression Temperat1re. l l '100F 70"B` 70 F. Pressure Atmos 380# ga 380# ga. Analysis:

' Air. 35% (mol) 93% (mol) Propane i Butane. l 40 61 61% (mol). Pentane 23.

Hexaiie-i- 1 16.

Total 100.

Percentage on tank vapors 35% 65%.

l 7% hydrocarbon falls in explosive limit andis unsafe.' Operation 2 (Recycle of segregated constituents) IntervRecovered Tank mediate Residue gas gasoline after va `0rs recycle after corncompression i p gas pression and stabilistream zation Temperature.- 100 F 100 F... 70 F 70 F. Pressure Atmos Atmos-- (350# ga' 350# ga. Analysis:

Air 35% (mol) Propane Butane 40 61% (mol). Pentane." 23% (mol). Hexane+ 16% (mol).

Total 100 100.

Percentage Von .t

tank vapors. 100% 25% 65% 35%.

1 17%vhydro'carbon well outside explosivelimit and is safe.

From the` foregoing it .is apparent that by following theprocessof the .presentinventiom the composition of the gases after compression is maintained well above the explosiveA limit without decreasing Y the recovery of gasoline fractions. Y 4 1 What I claim as new and wish to protect by Letters Patent is:

1. inthe handling-of V10W boiling hydrocarbons' by Vadding thereto vadditional Vair-free vaporized low boiling hydrocarbons in quantity sufficient to render said mixture explosionprooicompressing the resulting hydrocarbon-enriched mixture under conditions `to 4condense hydrocarbons therefrom, andreturningA said condensed hydro-` carbons to the storage tank.

2.Process according to claim l. in whichthe added hydrocarbons are secured by condensing hydrocarbons from the mixture of hydrocarbons vand air, removing uncondensed gases from -thel condensate, segregating from the condensate re1- atively` lower boiling hydrocarbons and adding said hydrocarbonsV to said gas mixture. l l

3. lProcess according to .claim:1, inwhich. theV lquantity of .hydrocarbons `added 'iswithin; the

range of 5 to 50% by volume based upon the v01- ume of vapors evolved from the tank.

4. In the handling of the vapors of low boiling hydrocarbons in admixture with substantial quantities of air produced in the breathing of 5 gasoline storage tanks, the improvement which comprises compressing the vapor-air mixture, cooling the compressed mixture to form a condensate, separating air therefrom, fractionating the condensate to produce vapors of 10W boiling hydrocarbons and a residual hydrocarbon liquid,

passing said vapors of low boiling hydrocarbons into the vapor-air mixture from the tank in quantity sufficient to place the same outside the explosive range prior to compression of the mixture, and returning the residual hydrocarbons to the tank.

5. Process according to claim 4, in which the quantity of hydrocarbons added is Within the range of 5 to 50% by volume based upon the vol- 10 ume of vapors evolved from the tank.

WALTER H. RUPP. 

